This invention relates generally to molecular medicine and autoimmune diseases and, more specifically, to methods for diagnosis of Graves' disease (GD).
The immune system is a complicated network of cells and molecules that normally work to defend the body and eliminate infections caused by bacteria, viruses, and other invading microbes. If a person has an autoimmune disease, the immune system mistakenly attacks self, targeting the cells, tissues, and organs of a person's own body. A collection of immune system cells and molecules at a target site is broadly referred to as inflammation.
Cells responsible for the specificity of the immune system are referred to as lymphocytes. Lymphocytes are a class of white blood cells. The antigen-specific immune system comprises a variety of differentiated T cells (thymus-derived lymphocytes) and B cells (bone-marrow-derived lymphocytes). Different categories and sub-categories of lymphocytes are defined by expression of different cell-surface antigens. Specifically, various categories and sub-categories of T cells have been identified by characteristic patterns of cell-surface antigen expression.
There are many different types of autoimmune diseases that each affect the body in different ways. For example, the autoimmune reaction is directed against the brain in multiple sclerosis and the gut in Crohn's disease. In other autoimmune diseases such as systemic lupus erythematosus, affected tissues and organs may vary among individuals with the same disease. Ultimately, damage to certain tissues by the immune system may be permanent, as with destruction of insulin-producing cells of the pancreas in Type 1 diabetes mellitus.
While the incidence of most individual autoimmune diseases is rare, as a group autoimmune diseases afflict millions of Americans. Most autoimmune diseases strike women more often than men; in particular, they affect women of working age and during their childbearing years.
In a number of autoimmune diseases including, for example, Graves' disease (GD), Rheumatoid Arthritis (RA), myasthenia gravis, insulin-resistant diabetes (Type I), antibodies to cell membrane receptors lead to anti-receptor hypersensitivity reactions that alter cellular function as a result of the binding of antibody to membrane receptors, which can have a stimulatory or a blocking effect. For example, in animal models of myasthenia gravis, the production of antibodies by immunization to the acetylcholine receptor has resulted in the typical muscle fatigue and weakness noted in affected humans, where this antibody has been shown to be present in serum and on muscle membranes and, further, prevents the binding of endogenously produced acetylcholine to its receptor, thereby preventing muscle activation. Similarly, in some diabetic individuals with extreme insulin resistance, antibodies to insulin receptors have been shown that prevent the binding of insulin to its receptor.
Graves' disease (GD) is a systemic autoimmune process characterized by several immune system abnormalities, including the production of IgG directed against the thyrotropin receptor, expansion of CD45RO+ T cells (Bossowski et al., J. Ped Endocrinol Metab 16:63-70 (2003)) and lymphocytic infiltration of the thyroid and connective tissue of the orbit (Akamizu et al. Endocrine J 44:633-646 (1997)). Thyroid-associated ophthalmopathy (TAO) represents the orbital manifestation of GD. Extra-ocular muscles and fat expand, become inflamed and are remodeled extensively (Akamizu et al. Endocrine J 44:633-646 (1997)). Cytokines and lipid mediators, synthesized by infiltrating T lymphocytes, monocytes and mast cells, drive tissue remodeling, including the accumulation of hyaluronan, an abundant non-sulfated glycosaminoglycan (Smith et al. Am J Physiol 268:C382-C388 (1995); Prabhakar et al., Endocrine Rev 24:802-835 (2003)). The unique phenotype of orbital fibroblasts and their exaggerated responses to cytokines such as IL-1β represent the basis for disease susceptibility of these tissues (Smith, supra, (1995), Wang et al., J Biol Chem 271:22718-22728 (1996); Young et al., Proc Natl Acad Sci (USA) 95:8904-8909 (1998); Han et al., J Biol Chem 277:16355-16364 (2002); Cao and Smith; Am J Physiol 277 (1999); Cao et al., J Biol Chem 273:29615-29625. (1998)). Why immunocompetent cells are recruited to the orbit in TAO remains uncertain.
For GD, the mechanism through which immunocompetent cells are trafficked to affected tissues is critical to understanding and, ultimately, to developing therapies that address both the glandular as well as the non-glandular manifestations of Graves' Disease. IGF-1R is expressed by a disproportionately large fraction of fibroblasts from individuals with GD (Pritchard et al., J Immunol 170:6348-6354 (2003)). When treated with IGF-1 or with IgG derived from these individuals (GD-IgG), GD fibroblasts, but not those from control donors, synthesize high levels of IL-16 and RANTES, two powerful T cell chemoattractants (Pritchard et al., supra, 2003). In addition, orbital fibroblasts from individuals with GD synthesize increased levels of hyaluronan when treated with GD-IgG, an action mediated by IGF 1R (Smith and Hoa., J Clin Endocrinol Metab 89:5076-5080 (2004)). Auto-antibodies directed against IGF-1R can be detected in almost all individuals with GD but in few individuals without the disease (Pritchard et al., J Immunol 170:6348-6354 (2003); Smith and Hoa., J Clin Endocrinol Metab 89:5076-5080 (2004); Smith, Autoimmunity 36:409-415 (2003).
The insulin-like growth factor receptor (IGF-1R) pathway plays important and diverse roles in growth and development (Benito et al., Horm Res 66:221-230 (1996)). This tyrosine kinase receptor has been implicated in several metabolic, neoplastic and immunological diseases (Walenkamp and Wit, Horm Res 66:221-23 (2006); Kurmasheva and Houghton; Biochim Biophys Acta 1766:1-22 (2006); Bateman and McNeill, Cell Mol Life Sci 63:1701-1705 (2006).). IGF-1R and associated IGF-1 binding proteins constitute a cell surface signaling complex (De Meyts et al., Novartis Found Symp 262:160-171 (2004); Li and Miller, J Biol Chem 281:23785-23791 (2006)). An IGF-1 binding domain resides in the extracellular domain of IGF-1Rα while three tyrosine residues represent auto-phosphorylation sites, namely Tyr1131, Tyr1135, and Tyr1136, within the activation loop of the IGF-1R β catalytic domain (Li and Miller, supra, 2006)). Phosphorylation at all three is required for optimal receptor activation. This culminates in the recruitment of multiple docking proteins and the generation of intracellular signaling (De Meyts et al., Novartis Found Symp 262:160-171 (2004).
IGF-1 and IGF-1R play important roles in hematopoietic cell growth and differentiation and normal immune function (Zumkeller, W. Leuk Lymphoma 43:487-491 (2002)). Peripheral blood T and B cells and monocytes from control human donors express low levels of IGF-1R in vivo (Kooijman et al., Endocrinology 131:2244-2250 (1992); Kooijman et al., Eur J Immunol 25:931-935 (1995)). Administration of IGF-1 increases the circulating pool of CD4+ T cells and splenic B cells in mice (Clark et al., J Clin Invest 92:540-548 (1993); Jardieu, et al., J Immunol 152:4320-4327 (1994)), suggesting a role for this growth factor in myelopoietic cell expansion (Alpdogan et al., Transplantation 75:1977-1983 (2003)). It promotes T cell proliferation during early activation (Hettmer et al., Hum Immunol 66:95-103 (2005)) and inhibits apoptosis of both immature and mature T cells through at least three distinct mechanisms (Liu et al., Pediatr Res 54:919-925 (2003); Navarro and Baserga, Endocrinology 142:1073-1081 (2001)). IGF-1 stimulates inflammatory cytokine production in T cells and monocytes, including IL-2 (Kooijman et al., J Endocrinol 149:351-356 (1996)), TNF-α (Renier et al., Endocrinology 137:4611-4618 (1996)) and IL-8 (Kooijman et al. Cell Signal 15:1091-1098 (2003)). It can bias lymphocyte development toward a Th2 phenotype by enhancing IL-10 (Kooijman and Coppens; J Leukoc Biol 76:862-867 (2004)), IL-4, and IL-13 synthesis (Wynes and Riches; J Immunol 171:3550-3559 (2003)) while inhibiting IFN-γ function (Bemabei et al., Blood 102:2933-2939 (2003)). With regard to B cell differentiation, IGF-1 promotes immunoglobulin production in chimeric immunodeficient mice reconstituted with IGF-1R−/− fetal liver cells (Baudler et al., J Immunol 174:5516-5525 (2005)). It also enhances T cell-independent humoral immune responses (Baudler et al., supra, 2005). These findings indicate that functional IGF-1R may be required for T cell independent B cell responses and support its important role in B cell differentiation and antibody production.
Thus, there exists a need for identification of immune system components that are implicated in the IGF-1R mediated autoimmune response. The present invention satisfies this need and provides related advantages as well.